1. Field of the Invention
The invention relates to a semiconductor composite device including a driven element such as a light-emitting thyristor and a driving circuit configured to drive the driven element, a method of manufacturing the semiconductor composite device, an optical print head including the semiconductor composite device, and an image forming apparatus such as an electrophotographic printer including the optical print head.
2. Description of Related Art
There has been known a conventional image forming apparatus such as an electrophotographic printer including an exposure device wherein plural light-emitting elements are arrayed. A light-emitting diode (hereinafter, referred to as a “LED”), an organic electroluminescence (hereinafter, referred to as an “organic EL”), a light-emitting thyristor, or the like is used as the light-emitting element.
In an art using a light-emitting thyristor, a driving circuit and the light-emitting thyristor(s) are provided in one-to-one or one-to-N (N<1). The light-emitting thyristor is controlled to be on or off, by switching on or off a driving current between the anode terminal (hereinafter, simply referred to as an anode) and the cathode terminal (hereinafter, simply referred to as a cathode) of the light-emitting thyristor. The emission energy (illumination intensity) of the light-emitting thyristor is determined by the value of the driving current. That is, the energy of light exposed from an exposure device having the light-emitting thyristors to a photosensitive drum is determined by the value of the driving current.
Since the light-emitting thyristor is generally formed of a compound semiconductor, it is inevitable that the illumination intensity of the light-emitting thyristors varies due to crystal defects in the compound semiconductor. Accordingly, non-uniform print density may occur in an image forming apparatus using the light-emitting thyristors made of the compound semiconductors. To solve this problem, there has been known a related art wherein an illumination intensity correction is executed by separately controlling the value of a driving current for each of light-emitting thyristors.
Japanese Patent Application Laid-Open No. 2007-81081 discloses a manufacturing method of a semiconductor composite device. In the manufacturing method, an epitaxial film (hereinafter, referred to as an “epi film”) is used. The epi film is formed by providing an epitaxial layer on a GaAs base member, forming a light-emitting thyristor within the epitaxial layer, and delaminating the epitaxial layer from the GaAs wafer base member to obtain a film as the epi film. The epi film is attached on a silicon wafer in which a driving circuit is formed. Then, the light-emitting thyristor and the driving circuit are electrically connected to each other with thin film wires. With this process, a semiconductor composite device in which the light-emitting thyristor and the driving circuit are integrated is obtained.
However, the conventional semiconductor composite device and the manufacturing method have the following problems (a) and (b).
(a) The semiconductor composite device is manufactured by: forming first metal wires by a photo-lithography method to electrically connect circuit elements of the driving circuit which were previously formed in the silicon wafer; attaching the epi film having therein the light-emitting thyristors onto the silicon wafer; and then forming second metal wires to electrically connect output terminals of the driving circuit to gates of the light-emitting thyristors. Accordingly, the two metal wire wiring steps are needed to manufacture the semiconductor composite device, and this increases the manufacturing cost.
(b) Since the first metal wires for the driving circuit are thin films mainly made of aluminum, which does not have high heat-resistance, it is difficult to execute a high-temperature process such as an impurity diffusion process after the epi-file is attached on the wafer.